The present invention is for a new kind of ignition sparking device which replaces conventionally designed spark plugs. The device is especially suitable for the kind of combustion engines which are named counterstroke engines having two pistons which work against each other in a common cylinder bore.
In some kinds of combustion engines there are used sparking devices having two electrodes between which there is a discharge, once during each working cycle. One electrode can be directly connected to the engine block while the other electrode is insulated from the engine block. The two electrodes are made from metal and special alloys have been developed for this purpose. A spark plug of conventional design is inserted into the cylinder through a threaded hole especially made for this purpose. One electrode is usually designed as a straight pin through an insulating body while the other electrode protrudes from a metallic housing around the insulated body so that the tip of the second electrode extends below and beyond the first electrode.
There are several factors which influence the function of the sparking device and the combustion process. Such factors which are directly connected to the design of the sparking device are the distance between the electrodes in the area of discharge and the position of the electrodes in the combustion space especially in relation to the top of the pistons at each occasion of combustion. Other factors are the temperature of operation of the engine and the composition of the fuel air mixture. Various conditions in this respect give rise to different requirements from the sparking device and the design of these which is finally chosen is at least in some respects a compromise between different requirements.
During the operation of the combustion engine the sparking device wears which appears as an increasing distance between the most adjacent parts of the electrodes in the so called spark gap. This causes a continues change of the conditions of operation and after a certain time the sparking device has to be dismounted and adjusted or exchanged. It is not possible to adjust the spark gap of conventional spark plugs during operation. The possibilities of adjustment are limited thereby that the electrodes extend in directions which are essentially at right angle to each other. Changes in the conditions of the operation means that these will not remain optimum for example from an environmental point of view or regarding the efficiency and capacity of the engine.